U.S. Pat. No. 9,443,180 is assigned to the present assignee and incorporated herein by reference. That patent discloses details of methods to print microscopic LEDs on a security label or directly on an object to be authenticated, where the LEDs are naturally randomly arranged within the security mark, such as within a 1 cm2 area. For example, there may be 30-50 LEDs within the security mark, and each security mark is inherently different. The LEDs are illuminated and the random pattern is stored in a database. Phosphor particles may instead be printed and illuminated with UV or a blue light. The security label is then attached to an object to be later authenticated. Any type of visible serial number or other object identifier may be paired with the stored random pattern in the security mark. For authentication, such as at the point of sale, the light emitting particles (LEDs or phosphor) are illuminated and the detected pattern is communicated to the database, such as via the Internet. If there is a match between the detected pattern and the previously stored pattern, the object is deemed to be authenticated. Some items mentioned that may be authenticated include bank notes, passports, high value products, and credit cards.
It is desirable to expand on the general concept of basing authentication on printed light emitting particles in order to provide security or to provide additional features that make use of the light emitting particles.